The broad, long-term objectives of this research are to make original contributions to scientific understanding of biological perception. The specific aims are to: 1) develop and test a causal model of touch sensations'integration with visual sensations for perception, and to generalize this model for application to a broader class of sensory integration phenomena, 2) apply causal models to investigate how humans perceive cause-and-effect events, 3) increase the applicant's technical proficiency with causal modeling and applied machine learning methods. The proposal includes two main projects;the first will measure how humans judge the size of objects when their distances are uncertain. Specifically the first project examines the theory that human perception uses knowledge about how size and distance sensations are caused to integrate related sensations. Human experimental participants will view objects while touching them and report their perceptions of the objects'sizes, which will be used to evaluate theoretical predictions. The second project investigates how humans perceive cause-and-effect chains of events by examining the theory that the brain uses built-in knowledge of rudimentary physical behaviors, like momentum in collisions, to interpret such simple events. Human experimental participants will view colliding objects and report what occurred, which will again be used to evaluate theoretical predictions. PUBLIC HEALTH RELEVANCE: The public health relevance of this research is to increase scientific and medical understanding of the neural communication and processing strategies the brain employs to create perceptual experiences, so that people with perceptual impairments can be provided with effective rehabilitation programs and biotechnological substitutes for diminished capabilities. Specific impairments include blindness and low-vision, traumatic brain and nervous system injuries, and strokes. In particular, modern sensory prostheses are now using computerized components that can interface with neural pathways to more comprehensively and effectively restore normal abilities in patients, and whose development faces significant obstacles establishing effective communication channels with the biological nervous system.